1. Field of the Invention
The present invention relates to a three-dimensional measuring device and a board inspection device equipped with this three-dimensional measuring device.
2. Background Art
When an electronic component is mounted on a printed circuit board, a cream solder is generally first printed on a specific electrode pattern disposed on the printed circuit board. Adhesivity of this cream solder is then used to temporarily fix the electronic component on the printed circuit board. Thereafter, the above-described printed circuit board is conveyed to a reflow furnace, and soldering is performed by a routine reflow process. Recently, it has become necessary to perform an inspection of the printed state of the cream solder at a stage prior to conveyance to the reflow furnace, and three-dimensional measuring devices have been used for such inspection.
Various types of so-called non-contact type three-dimensional measuring devices using light have been proposed in recent years. Among these types, technology has been proposed that relates to three-dimensional measuring devices utilizing the phase shift method (e.g., see Patent Citation 1 and the like). In a three-dimensional measuring device using this phase shift method, an irradiation means is used that combines a light source and a sine wave pattern filter, and this irradiation means illuminates the printed circuit board using a light pattern having a sinusoidal (stripe shaped) light intensity distribution. Thereafter, points on the circuit board are measured using a CCD camera or the like disposed directly above the circuit board. In this case, intensity I of light at a point P on the measurement object in the image is given by the following equation:I=e+f×cos(φ)
(within the formula, e=direct current optical noise (offset component), f=sine wave contrast (reflectivity), and φ=phase imparted by unevenness of the object).
At this time, the light pattern is moved and the phase is changed, for example, in four stages (e.g., φ+0, φ+π/2, φ+π, and φ+3π/2). Images having intensity distributions corresponding to these phase shift changes (e.g., I0, I1, I2, and I3, respectively) are captured, and the modulation component α is determined based on the formula below.α=arctan {(I3−I1)/(I0−I2)}
This modulation component α can be used to determine the three-dimensional coordinates (X, Y, Z) at the point P on the measurement object, such as cream solder or the like, and these three-dimensional coordinates are used to measure the three-dimensional shape of the cream solder and particularly to measure height of the cream solder.
However, actual measurement objects include both tall measurement objects and short measurement objects. For example, in the case of cream solders, there are both thin film-shaped cream solders and protruding cream solders which form a truncated cone shape. If the gaps between the lines of the irradiated light pattern are widened in order to adjust to the maximum height among such measurement objects, resolution ability becomes poor, and there is concern that measurement accuracy will worsen. On the other hand, although attempting to improve accuracy may be possible by narrowing the gaps between the lines, this then results in concern that the height range which is capable of measurement would become insufficient (such narrow gaps would result in errors due differences in line orders).
Therefore, combining the above-described phase shift method with the spatial encoding method has been proposed to obtain a large height range capable of measurement while also attaining highly accurate measurement (e.g., see Patent Citation 2).    Patent Citation 1: Japanese Unexamined Laid-open Patent Application No. H11-211443    Patent Citation 2: Japanese Unexamined Laid-open Patent Application No. H11-148810
However, according to the technology described in Patent Citation 2, a previously determined number of imaging operations must be performed even if the spatial encoding method is used in addition to the phase shift method, and this necessarily invites an increase in the number of imaging operations. For this reason, there has been concern that this technology invites an overall lowering of processing speed and the need for more time during measurement.
In consideration of the above-described circumstances, the object of the present invention is to provide a three-dimensional measuring device and a board inspection device capable of increasing the height range capable of measurement, attaining highly accurate measurement, and suppressing the number of imaging operations to a minimum, thereby attaining an improvement of efficiency of measurement (or inspection).